The field of the invention relates to idle speed control systems for internal combustion engines. In particular, the field relates to idle speed control systems for direct injection spark ignition engines.
Direct injection spark ignition engines are known in which the combustion chambers contain stratified layers of different air/fuel mixtures. The strata closest to the spark plug contains a stoichiometric mixture or a mixture slightly rich of stoichiometry, and subsequent strata contain progressively leaner mixtures. The strata near the plug is ignited which in turn ignites the leaner strata thereby achieving very lean overall operation and, therefore, enhanced fuel economy.
The inventors herein have recognized numerous problems when controlling idle speed of direct injection spark ignition engines. For example, prior approaches lack the ability of optimizing lean operation and concurrently avoid rough idling conditions.